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MODERN PENETROMETER TESTING FOR SOIL INVESTIGATION AND FOUNDATION DESIGN

A MECHANICAL AND AN ELECTRICAL TESTING CONE ARE DESCRIBED AND ILLISTRATED. A COMPARISON OF TESTS USING THE TWO TYPES OF EQUIPMENT SHOWS THAT (1), THE CONTINUOUS RECORD OF CONE RESISTANCE IN THE ELECTRICAL METHOD PROVIDES MORE DETAILS ON THE NATURE OF SUBSOIL THAN DOES THE MECHANICAL METHOD; (2), FRICTION BETWEEN THE INNER AND OUTER RODS IN THE MECHANICAL METHOD INFLUENCES THE READINGS AND GIVES INCORRECT RESULTS - FRICTION IS ABSENT IN THE ELECTRICAL METHOD AS NO INNER ROD IS USED; (3) THE ELECTRICAL METHOD PRODUCES A SOUNDING GRAPH AT THE CORRECT SCALE, WHEREAS-THE MECHANICAL METHOD PROVIDES ONLY A SET OF READINGS WHICH THEN HAVE TO BE CALCULATED AND PLOTTED. SEMI-AUTOMATIC EQUIPMENT DEVELOPED FOR UNDER WATER PENETROMETER TESTING IS DESCRIBED TOGETHER WITH A DEVICE DEVELOPED BY FUGRO WHICH IS INCORPORATED IN THE CONE AND MEASURES THE DEVIATION FROM THE VERTICAL OVER THE FULL DEPTH OF THE PENETRATION TEST. EXPERIENCE IN THE NETHERLANDS HAS SHOWN THE CONE TEST TO BE QUICKER AND VERY MUCH CHEAPER THAN BORING, FOR IN SITU SOIL INVESTIGATION. /RRL/